The present invention relates to a diagnosis system for a motor vehicle.
Recently, a motor vehicle was equipped with an electronic control system for controlling various components of an engine, such as fuel injectors, thereby improving driveability, exhaust gas emission, fuel consumption and engine power. The electronic control system controls the components based on information represented by output signals from various sensors for detecting engine operating conditions. Accordingly, if malfunctioning of the components and sensors occur, the engine does not properly operate.
However, because of complexity of the electronic control system, it is difficult to immediately recognize the trouble. Accordingly, a trouble diagnosis device for easily checking the electronic control system should be equipped in an auto shop. The electronic control system has a memory and a communication system to be connected to the trouble diagnosis device.
Japanese Utility Model Application Laid-Open 60-25974 discloses a diagnosis system in which a plurality of connectors are provided between various sensors and control circuits or between various actuators and control circuits. A plurality of decision circuits, holding means and displays are connected to the connectors for detecting an abnormality of the system. Since a plurality of connectors, decision circuits holding means and displays are provided, the system becomes complicated in structure.
Recently, a diagnosis system has been proposed, in which a bidirectional communication system is provided between the electronic control system and the trouble diagnosis device, thereby diagnosing data based on output signals from various sensors and control data for various actuators in the control system through a single diagnosis device.
However, in a motor vehicle, a plurality of electronic control systems for the engine, transmission, brake and cruise are provided. In order to diagnose trouble in these control systems, connectors for respective control systems must be connected to a connector of the diagnosis device, which is troublesome work. When a plurality of control systems are in trouble at one time, it is difficult to diagnose those troubles and it takes time to determine the trouble.